1. Field of the Invention
The present invention relates to an internal combustion engine, particularly of the high output type.
2. Description of the Prior Art
Internal combustion engine intake and exhaust valves have heretofore been made of heat resisting steel. It is a usual practice to provide each engine cylinder with two valves, i.e., one intake valve and one exhaust valve. However, in some internal combustion engines for automotive vehicles or autobicycles, each engine cylinder is provided with more than three valves in order to attain a high output and a high operating efficiency.
It has recently been tried to utilize valves made of ceramics for reducing the weight of the valve train and thereby improving the responsiveness and increasing the maximum output and the operating efficiency.
The engine rpm at which so-called "valve surging" occurs is usually determined by the weight of the heaviest valve. The "valve surging" is a kind of vibration or jumping of a valve resulting from a resonance phenomena of a valve train including a valve, valve spring, tappet, etc. Accordingly, in order to prevent "valve surging" , it is useful to employ the intake valve or valves made of ceramics. The intake valve or valves made of ceramics are designed to be larger than the exhaust valve or valves.
However, if the intake valve or valves made of ceramics should chip, the chipped piece or pieces would enter another cylinder to break the valves thereof, thus resulting in a high possibility of the engine becoming inoperative. Accordingly, it is undesirable for safety reason to employ the intake valve or valves made of ceramics.